Poster Presentation Astronomical Society of Australia Annual Scientific Meeting including HWWS 2013

Discovery of the oldest stars in the Galactic bulge (#228)

Louise M Howes 1 , Martin Asplund 1 , Stefan Keller 1
  1. Australian National University, Weston, ACT, Australia

Despite frequent attempts over many years, the elusive first stars of the Universe have yet to be found.  Searches for these "Population III" objects have targeted the old and metal-poor Galactic halo.  However according to models of the formation of galaxies like the Milky Way, the oldest stars should lie in the centre of the Galaxy - in the bulge.

Until now, problems with overcrowding and extinction have made searching the bulge an impossible task; the most metal-poor star previously known has [Fe/H]=-2.1.  Our dedicated search, using SkyMapper photometry to pre-select low metallicity candidates, will discover >100 bulge stars with [Fe/H]<-3, all confirmed using AAOmega on the AAT.

Here we present the first results of the ongoing survey: >2000 stars with [Fe/H]<-1, and from the pilot study, high-resolution spectroscopy of 12 stars (8 with MIKE on Magellan, and 4 as part of the Gaia-ESO survey using FLAMES UVES on the VLT).  These high-resolution data have confirmed the discovery of the bulge's most metal-poor stars yet. They have allowed us to derive detailed chemical abundances of these stars, including alpha and s-process elements, which we have compared to the other components of the Galaxy.  At the time of writing, we are currently following up another 8000 candidates with 9 nights at the AAT, the exciting results of which will be described on our poster!